CVE-2026-31937: 
Suricata vulnerability analysis and mitigation

CVE-2026-31937 is a denial-of-service vulnerability in Suricata, the open-source network IDS, IPS, and NSM engine, caused by quadratic complexity in DCERPC (Distributed Computing Environment/Remote Procedure Call) buffering. An unauthenticated remote attacker can send specially crafted network traffic to trigger the inefficient buffering mechanism, resulting in significant performance degradation of the Suricata engine. All Suricata versions prior to 7.0.15 are affected. The vulnerability was published on April 2, 2026, and carries a CVSS v3.1 base score of 7.5 (High) (GitHub Advisory, Red Hat Bugzilla).

The root cause is classified under CWE-407 (Inefficient Algorithmic Complexity) and CWE-770 (Allocation of Resources Without Limits or Throttling), specifically a quadratic-complexity algorithm in Suricata's DCERPC protocol parser buffering logic. An attacker with network access can craft DCERPC traffic that triggers worst-case buffering behavior, causing CPU or memory resource exhaustion without requiring any authentication or user interaction. The vulnerability was discovered by OSS-Fuzz and is tracked internally at the Open Information Security Foundation (OISF) as issue #8304 (GitHub Advisory, OISF Redmine).

Successful exploitation causes a denial-of-service condition by degrading or disabling Suricata's network monitoring, intrusion detection, and intrusion prevention capabilities. There is no confidentiality or integrity impact; the sole consequence is high availability impact to the Suricata engine itself. In environments where Suricata operates as an inline IPS, exploitation could effectively blind the network security monitoring infrastructure, potentially allowing other malicious traffic to pass undetected (GitHub Advisory, Red Hat Bugzilla).

There is no public proof-of-concept exploit code and no evidence of in-the-wild exploitation at this time. The EPSS score is approximately 0.04%, reflecting a low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported (GitHub Advisory).

1. Reconnaissance: Identify network segments monitored by Suricata instances running versions prior to 7.0.15, potentially by observing DCERPC traffic handling or querying exposed management interfaces.
2. Craft malicious DCERPC traffic: Generate specially crafted DCERPC protocol messages designed to trigger worst-case quadratic buffering behavior within Suricata's DCERPC parser.
3. Transmit traffic: Send the crafted DCERPC packets across the network segment being monitored by the target Suricata instance — no authentication is required.
4. Trigger performance degradation: The inefficient buffering algorithm processes the crafted input with quadratic complexity, consuming excessive CPU or memory resources and causing Suricata to degrade or become unresponsive (GitHub Advisory).

• Network: Unusual volumes of DCERPC protocol traffic (typically over TCP port 135 or dynamic RPC ports) directed at monitored network segments; repeated or malformed DCERPC PDUs with abnormally large or deeply nested payloads.
• Process: Suricata process exhibiting sustained high CPU usage or memory growth without a corresponding spike in legitimate traffic volume; Suricata worker threads becoming unresponsive.
• Logs: Suricata stats logs showing a sharp drop in packet processing throughput or increased packet drop rates; error or warning messages related to DCERPC parser resource limits in suricata.log.

Upgrade Suricata to version 7.0.15 or later (also fixed in version 8.x), which contains the patch for this vulnerability (GitHub Advisory). As a temporary workaround where immediate upgrade is not possible, disable the dcerpc application layer parser in the Suricata configuration (suricata.yaml) by setting dcerpc to no under app-layer.protocols. Organizations running Suricata as an inline IPS should prioritize patching given the potential for this vulnerability to blind network security monitoring.

The Suricata project released versions 8.0.4 and 7.0.15 simultaneously on March 17, 2026, addressing this and other issues, with an announcement on the official Suricata forum and website (Suricata Release). Red Hat tracked the issue via Bugzilla and classified it as high severity (Red Hat Bugzilla). openSUSE issued a security announcement to its mailing list, and the vulnerability received coverage from several CVE aggregation and threat intelligence platforms.